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Susan Burgmaier <br />C -1996 -083 TR -85 PAR No. 2 - Geotechnical <br />21 -Feb -2014 <br />Page 3of4 <br />storage area. I believe that BRL's intention should be clearly stated: either damage to <br />VWP -06 will be avoided (will a vertical extension of the pipe be required ?), or is damage <br />to this instrument likely or expected? If the latter is true, then plans and commitments <br />for its replacement should be made at this time. We have only two functioning <br />piezometers remaining in the upper reaches of CMWDA No. 2. Given the slow rate at <br />which the pile is dewatering, I believe it is imperative that collection of pore pressure <br />data not be interrupted. <br />3. MLT 01/09: Buckhorn's Model #1, a 15 -foot pile at 1.5h :1v, results in a Factor of Safety (FoS) of <br />essentially 1.0, which implies that slippage of material down the slope is imminent at all times. <br />While this slope configuration may be acceptable on the sides of the Drying Area, the Division <br />questions whether this is appropriate for the front face of the pile, where a commitment has <br />been made to maintain a 25 -foot buffer. Continual sloughing from the face of the Drying Area <br />pile may produce a maintenance challenge. <br />MLT 02/21: Buckhorn responded that BRL's surface operations staff will maintain the 25 -foot <br />buffer, and that no changes to the design are proposed. That may be the case. However, the <br />stability analysis assumes a 25 -foot setback. If there is a chance that material may encroach <br />upon the buffer, please evaluate the effect on the stability of the pile as a whole if the setback is <br />not maintained. <br />4. MLT 01/09: In the Results Discussion section, Buckhorn refers to the long term FoS of 1.5 <br />required by Rule 4.09.1. That rule is specific to disposal of excess spoil. For Coal Mine Waste <br />Banks, Rule 4.10.4(2) applies, which requires a minimum static safety factor of 1.5 (not limited <br />to the "long term" condition). Please revise this paragraph to reference Rule 4.10.4(2) rather <br />than 4.09.1. (The Division concurs that the Drying Area itself need not be held to a FoS of 1.5; <br />what is proposed with TR -85 represents a significant improvement in the handling of wet CMW <br />over methods used historically at the site.) <br />MILT 02/21: Buckhorn's response includes the proper citation. This item is resolved. However, <br />a new, related issue is incorporated here: <br />a) For permanent inclusion into Volume IX of the permit, the two documents submitted by <br />Buckhorn (05 -Dec -2013 and 04- Feb -2014) should be replaced by a single comprehensive <br />report which also addresses the issues raised in this latest adequacy review. <br />5. MLT 01/09: For Volume IX, the Table of Contents should be updated to show the revised page <br />numbering and the addition of a new Buckhorn Geotech analysis. <br />MLT 02/21: The TOC was updated, as requested, but will require an additional revision (see <br />Item 4a, above). Volume IX should also be revised to include an earlier Buckhorn report, dated <br />February 15, 2006. That stability evaluation was prepared for TR -42, which was subsequently <br />withdrawn. However, the Feb -2006 report has been consistently referenced by subsequent <br />Buckhorn papers, and includes some information that is not available in later studies. <br />6. This item has been addressed. <br />